The HD2 can do many things, and we can now add detect your surroundings to the list. The metal detecting application is still in the beta stage. Created where many good things come from, XDA. This freeware is a pretty nice app that brings many cool things to the device.
The application works in a very simple way. It takes the compass(This works by detecting the magnetic field in the north pole) in the HD2 is used to detect any metal object in its vicinities.
This application still has many bugs, but like many things, it will be fixed over time.